I blogged last week about the inherent YA appeal of Ayn Rand (and I think Literaticat got close to the reason in her comment). This piece from NPR's On the Media (a show everyone should listen to weekly) puts it into further perspective. It's worth the hearing the whole 13-minute bit, but the YA stuff is toward the end.
Why do I think this is interesting? Because I think it's worthwhile to examine books that appeal to teens that are manifestly not YA in any sense we use the term now. I am not a secret Rand fanboy.